WestJet's pilots have voted by a large margin against an agreement that would allow the airline to expand its wide-bodied fleet and its long-haul operations.

There were two potential agreements up for a vote, with 80 per cent of pilots voting against a memorandum of agreement that would have offered more hourly pay for all pilots and higher pay for those who flew wide-bodied jets, but converted stock options to base pay.

A second agreement that allowed pilots to retain their stock options and offered more pay only to those who flew wide-bodied jets, was also voted down, but by a much smaller margin of 57 per cent.

"We are disappointed in the outcome of the vote," said WestJet spokeswoman Lauren Stewart. "And we'll be meeting with the WestJet Pilot Association over the coming weeks to determine next steps."

WestJet launched a trial of wide-bodied 767 jets this past spring, with four aircraft flying to London's Gatwick Airport. Flights were heavily booked, but dealt with many mechanical problems over the spring, summer and fall, causing delays, cancellations and diversions. The average age of the jets was 24 years.

The airline said in its earnings call earlier this month that it wanted to expand the fleet, and had signed a deal with pilots to do so, but that the agreement needed to be ratified.